Improve example Caddyfile
Update the example Caddyfile to include features from the example Nginx config. This includes:
- Gzip
- HTTP security headers
- Cache directive for mediaproxy
Other additions:
- Include path for error logs
- Use only ciphers which are allowed for HTTP2
- Use an ECC key for the certificate
- Mention that the cache and cors directive need the corresponding plugin in the Caddy binary